MyBatisSpring Boot实战:数据库操作

  上篇著作中早已因此一个简易的HelloWorld程序讲解了Spring
boot的基本原理和运用。本文首要讲师如何通过spring
boot来访问数据库,本文会以身作则二种艺术来拜访数据库,第一种是JdbcTemplate,第二种是JPA,第三种是Mybatis。此前早已涉及过,本体系会以一个博客系统作为讲解的根底,所以本文会讲课作品的囤积和走访(但不包括随笔的详情),因为最后的实现是通过MyBatis来完成的,所以,对于JdbcTemplate和JPA只做简单演示,MyBatis部分会全部兑现对著作的增删改查。

一、准备干活

  在示范这两种方法从前,需要先准备一些东西。第一个就是数据库,本系统是应用MySQL实现的,大家需要先制造一个tb_article的表:

DROP TABLE IF EXISTS `tb_article`;

CREATE TABLE `tb_article` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `title` varchar(255) NOT NULL DEFAULT '',
  `summary` varchar(1024) NOT NULL DEFAULT '',
  `status` int(11) NOT NULL DEFAULT '0',
  `type` int(11) NOT NULL,
  `user_id` bigint(20) NOT NULL DEFAULT '0',
  `create_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `public_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

  后续的演示会对那一个表举办增删改查,我们应该会合到这多少个表里面并不曾成文的详情,原因是作品的详情相比长,假诺放在那个表里面容易影响查询随笔列表的效率,所以作品的详情会独自存在其它的表里面。其它大家需要配置数据库连接池,这里我们运用druid连接池,此外配置文件使用yaml配置,即application.yml(你也足以应用application.properties配置文件,没什么太大的分别,假设对ymal不熟练,有趣味也得以查一下,相比简单)。连接池的布置如下:

spring:
  datasource:
    url: jdbc:mysql://127.0.0.1:3306/blog?useUnicode=true&characterEncoding=UTF-8&useSSL=false
    driverClassName: com.mysql.jdbc.Driver
    username: root
    password: 123456
    type: com.alibaba.druid.pool.DruidDataSource

  最终,我们还需要建立与数据库对应的POJO类,代码如下:

public class Article {
    private Long id;
    private String title;
    private String summary;
    private Date createTime;
    private Date publicTime;
    private Date updateTime;
    private Long userId;
    private Integer status;
    private Integer type;

}

  好了,需要准备的办事就这么些,现在起来兑现数据库的操作。

 

 二、与JdbcTemplate集成

  首先,我们先通过JdbcTemplate来访问数据库,那里只演示数据的插入,上一篇随笔中我们早已涉嫌过,Spring
boot提供了无数的starter来支撑不同的效应,要援助JdbcTemplate我们只需要引入下边的starter就足以了:

<dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>

  现在我们就足以因此JdbcTemplate来促成多少的插入了:

public interface ArticleDao {
    Long insertArticle(Article article);
}

@Repository
public class ArticleDaoJdbcTemplateImpl implements ArticleDao {

    @Autowired
    private NamedParameterJdbcTemplate jdbcTemplate;

    @Override
    public Long insertArticle(Article article) {
        String sql = "insert into tb_article(title,summary,user_id,create_time,public_time,update_time,status) " +
                "values(:title,:summary,:userId,:createTime,:publicTime,:updateTime,:status)";
        Map<String, Object> param = new HashMap<>();
        param.put("title", article.getTitle());
        param.put("summary", article.getSummary());
        param.put("userId", article.getUserId());
        param.put("status", article.getStatus());
        param.put("createTime", article.getCreateTime());
        param.put("publicTime", article.getPublicTime());
        param.put("updateTime", article.getUpdateTime());
        return (long) jdbcTemplate.update(sql, param);
    }
}

  我们透过JUnit来测试下面的代码:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes = Application.class)
public class ArticleDaoTest {

    @Autowired
    private ArticleDao articleDao;

    @Test
    public void testInsert() {
        Article article = new Article();
        article.setTitle("测试标题");
        article.setSummary("测试摘要");
        article.setUserId(1L);
        article.setStatus(1);
        article.setCreateTime(new Date());
        article.setUpdateTime(new Date());
        article.setPublicTime(new Date());
        articleDao.insertArticle(article);
    }
}

   要匡助方面的测试程序,也需要引入一个starter:

 <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
 </dependency>

  从下边的代码可以看看,其实不外乎引入jdbc的start之外,基本没有布置,这都是spring
boot的自行帮大家做到了配备的历程。下边的代码需要小心的Application类的职务,该类必须放在Dao类的父级的包中,比如这里Dao都位于com.pandy.blog.dao这么些包下,现在大家把Application.java这一个类从com.pandy.blog这一个包活动到com.pandy.blog.app这些包中,则汇合世如下错误:

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.pandy.blog.dao.ArticleDao' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1493)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1104)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585)
    ... 28 more

  也就是说,找不到ArticleDao的兑现,这是什么样来头吧?上一篇博文中咱们早已观察@SpringBootApplication这些注脚继承了@ComponentScan,其默认意况下只会扫描Application类所在的包及子包。因而,对于地点的不当,除了保持Application类在Dao的父包这种形式外,也得以指定扫描的包来缓解:

@SpringBootApplication
@ComponentScan({"com.pandy.blog"})
public class Application {
    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class, args);
    }
}

    

三、与JPA集成

  现在大家起始上课怎样通过JPA的艺术来促成数据库的操作。如故跟JdbcTemplate类似,首先,我们需要引入对应的starter:

<dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

  然后大家需要对POJO类扩充Entity的诠释,并指定表名(倘若不点名,默认的表名为article),然后需要指定ID的及其浮动策略,那一个都是JPA的知识,与Spring
boot无关,如若不精通的话可以看下JPA的知识点:

@Entity(name = "tb_article")
public class Article {
    @Id
    @GeneratedValue
    private Long id;
    private String title;
    private String summary;
    private Date createTime;
    private Date publicTime;
    private Date updateTime;
    private Long userId;
    private Integer status;
}

  最后,我们需要连续JpaRepository这一个类,这里我们贯彻了五个查询办法,第一个是切合JPA命名规范的询问,JPA会自行帮我们做到查询语句的转移,另一种办法是我们温馨实现JPQL(JPA补助的一序列SQL的查询)。

public interface ArticleRepository extends JpaRepository<Article, Long> {

    public List<Article> findByUserId(Long userId);

    @Query("select art from com.pandy.blog.po.Article art where title=:title")
    public List<Article> queryByTitle(@Param("title") String title);
}

  好了,咱们得以再测试一下上边的代码:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes = Application.class)
public class ArticleRepositoryTest {
    @Autowired
    private ArticleRepository articleRepository;

    @Test
    public void testQuery(){
        List<Article> articleList = articleRepository.queryByTitle("测试标题");
        assertTrue(articleList.size()>0);
    }
}

  注意,这里依旧存在跟JdbcTemplate类似的问题,需要将Application这一个启动类未于Respository和Entity类的父级包中,否则会出现如下错误:

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.pandy.blog.dao.ArticleRepository' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1493)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1104)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1066)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585)
    ... 28 more

  当然,同样也得以透过讲明@EnableJpaRepositories指定扫描的JPA的包,不过如故不行,还会油但是生如下错误:

Caused by: java.lang.IllegalArgumentException: Not a managed type: class com.pandy.blog.po.Article
    at org.hibernate.jpa.internal.metamodel.MetamodelImpl.managedType(MetamodelImpl.java:210)
    at org.springframework.data.jpa.repository.support.JpaMetamodelEntityInformation.<init>(JpaMetamodelEntityInformation.java:70)
    at org.springframework.data.jpa.repository.support.JpaEntityInformationSupport.getEntityInformation(JpaEntityInformationSupport.java:68)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getEntityInformation(JpaRepositoryFactory.java:153)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository(JpaRepositoryFactory.java:100)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository(JpaRepositoryFactory.java:82)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:199)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.initAndReturn(RepositoryFactoryBeanSupport.java:277)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet(RepositoryFactoryBeanSupport.java:263)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean.afterPropertiesSet(JpaRepositoryFactoryBean.java:101)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1687)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1624)
    ... 39 more

  那几个错误表达识别不了Entity,所以还索要通过声明@EntityScan来指定Entity的包,最终的安排如下:

@SpringBootApplication
@ComponentScan({"com.pandy.blog"})
@EnableJpaRepositories(basePackages="com.pandy.blog")
@EntityScan("com.pandy.blog")
public class Application {
    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class, args);
    }
}

 

四、与MyBatis集成

  最终,我们再看看怎么着通过MyBatis来实现数据库的拜访。同样大家依然要引入starter:

<dependency>
      <groupId>org.mybatis.spring.boot</groupId>
      <artifactId>mybatis-spring-boot-starter</artifactId>
      <version>1.1.1</version>
</dependency>

  由于该starter不是spring boot官方提供的,所以版本号于Spring
boot不相同,需要手动指定。

  MyBatis一般能够经过XML或者讲明的点子来指定操作数据库的SQL,个人相比较偏向于XML,所以,本文中也只演示了经过XML的法门来拜访数据库。首先,大家需要安排mapper的目录。我们在application.yml中举行配置:

mybatis:
  config-locations: mybatis/mybatis-config.xml
  mapper-locations: mybatis/mapper/*.xml
  type-aliases-package: com.pandy.blog.po

  这里配置紧要不外乎两个部分,一个是mybatis自身的一些配备,例如基本类型的别名。第二个是指定mapper文件的地方,第多少个POJO类的别名。这些布局也可以透过
Java
configuration来落实,由于篇幅的题目,我这里就不详述了,有趣味的朋友可以友善实现一下。

  配置完后,我们先编制mapper对应的接口:

public interface ArticleMapper {

    public Long insertArticle(Article article);

    public void updateArticle(Article article);

    public Article queryById(Long id);

    public List<Article> queryArticlesByPage(@Param("article") Article article, @Param("pageSize") int pageSize,
                                             @Param("offset") int offset);

}

  该接口暂时只定义了六个法子,即添加、更新,以及基于ID查询和分页查询。这是一个接口,并且和JPA类似,可以毫无实现类。接下来大家编辑XML文件:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.pandy.blog.dao.ArticleMapper">

    <resultMap id="articleMap" type="com.pandy.blog.po.Article">
        <id column="id" property="id" jdbcType="INTEGER"/>
        <result column="title" property="title" jdbcType="VARCHAR"/>
        <result column="summary" property="summary" jdbcType="VARCHAR"/>
        <result column="user_id" property="userId" jdbcType="INTEGER"/>
        <result column="status" property="status" jdbcType="INTEGER"/>
        <result column="create_time" property="createTime" jdbcType="TIMESTAMP"/>
        <result column="update_time" property="updateTime" jdbcType="TIMESTAMP"/>
        <result column="public_time" property="publicTime" jdbcType="TIMESTAMP"/>
    </resultMap>

    <sql id="base_column">
      title,summary,user_id,status,create_time,update_time,public_time
    </sql>

    <insert id="insertArticle" parameterType="Article">
        INSERT INTO
        tb_article(<include refid="base_column"/>)
        VALUE
        (#{title},#{summary},#{userId},#{status},#{createTime},#{updateTime},#{publicTime})
    </insert>

    <update id="updateArticle" parameterType="Article">
        UPDATE tb_article
        <set>
            <if test="title != null">
                title = #{title},
            </if>
            <if test="summary != null">
                summary = #{summary},
            </if>
            <if test="status!=null">
                status = #{status},
            </if>
            <if test="publicTime !=null ">
                public_time = #{publicTime},
            </if>
            <if test="updateTime !=null ">
                update_time = #{updateTime},
            </if>
        </set>
        WHERE id = #{id}
    </update>

    <select id="queryById" parameterType="Long" resultMap="articleMap">
        SELECT id,<include refid="base_column"></include> FROM tb_article
        WHERE id = #{id}
    </select>

    <select id="queryArticlesByPage" resultMap="articleMap">
        SELECT id,<include refid="base_column"></include> FROM tb_article
        <where>
            <if test="article.title != null">
                title like CONCAT('%',${article.title},'%')
            </if>
            <if test="article.userId != null">
                user_id = #{article.userId}
            </if>
        </where>
        limit #{offset},#{pageSize}

    </select>
</mapper>

  最终,我们需要手动指定mapper扫描的包:

@SpringBootApplication
@MapperScan("com.pandy.blog.dao")
public class Application {
    public static void main(String[] args) throws Exception {
        SpringApplication.run(Application.class, args);
    }
}

  好了,与MyBatis的购并也大功告成了,我们再测试一下:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes = Application.class)
public class ArticleMapperTest {

    @Autowired
    private ArticleMapper mapper;

    @Test
    public void testInsert() {
        Article article = new Article();
        article.setTitle("测试标题2");
        article.setSummary("测试摘要2");
        article.setUserId(1L);
        article.setStatus(1);
        article.setCreateTime(new Date());
        article.setUpdateTime(new Date());
        article.setPublicTime(new Date());
        mapper.insertArticle(article);
    }

    @Test
    public void testMybatisQuery() {
        Article article = mapper.queryById(1L);
        assertNotNull(article);
    }

    @Test
    public void testUpdate() {
        Article article = mapper.queryById(1L);
        article.setPublicTime(new Date());
        article.setUpdateTime(new Date());
        article.setStatus(2);
        mapper.updateArticle(article);
    }

    @Test
    public void testQueryByPage(){
        Article article = new Article();
        article.setUserId(1L);
        List<Article> list = mapper.queryArticlesByPage(article,10,0);
        assertTrue(list.size()>0);
    }
}

  

五、总结

    本文演示Spring
boot与JdbcTemplate、JPA以及MyBatis的购并,全体上来说配置都相比简单,以前做过有关部署的同桌应该感到相比分明,Spring
boot确实在这地点给大家提供了很大的帮扶。后续的稿子中我们只会使用MyBatis这一种办法来进展数据库的操作,这里还有一些内需表明一下的是,MyBatis的分页查询在此间是手写的,这一个分页在专业开发中得以经过插件来成功,不过那些与Spring
boot没怎么关联,所以本文暂时通过这种手动的办法来开展分页的拍卖。

 

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